Does a jocular pronouncement of divorce upon the wife before consummation take effect, and what must the husband do?

A divorce pronounced in jest is effective. So long as you explicitly pronounced divorce without coercion, it has taken effect. Your ignorance of its ruling does not prevent it from taking effect.

If the divorce occurred after the marriage contract but before consummation, it is an irrevocable divorce (ṭalāq bā’in), and you do not have the right to take her back. If you wish to return to her, a new marriage contract, complete with all its pillars and conditions, is necessary.